MAPT and Alzheimer disease: To investigate the functional role of TREM2 on AD pathology, several studies have tested the impact of TREM2 deficiency on Aβ accumulation and tau pathology using various transgenic mouse models of AD as AD associated TREM2 mutations were assumed to result from TREM2 loss-of-function phenotype (Cheng-Hathaway et al., 2018; Song et al., 2018).